Reconstructive surgery is based upon the principle of replacing defective tissues with viable, functioning alternatives. In orthopaedic reconstruction, surgeons often replace damaged tissue resulting from trauma, pathological degeneration, or congenital deformity with autogenous grafts. The grafting of bone in skeletal reconstruction has become a common task of the orthopaedic surgeon with over 863,200 grafting procedures performed each year in the U.S. There are over 1,000,000 procedures of various types for cartilage repair performed each year and there are approximately 200,000 to 250,000 procedures for ligament repair performed per year (Langer and Vacanti, Science, 260 (5110):920-6 (1993)). Currently, autografts (tissue taken from the patient) and allografts (tissue taken from a cadaver) are the most common replacement sources for the treatment of musculoskeletal problems (Friedman, et al. Clin. Ortho., 196:9-14 (1985); Jackson, et al. Amer. J. Sports Med., 18 (1):1-10 (1990); Gazdag, et al. J. Amer. Acad Ortho. Surg., 3 (1):1-8 (1995); Shino et, al. J. Bone and Joint Surg., 70 (4)1:556 (1988) and Jackson, et al. Arthroscopy, 10:442-52 (1994)). In repair of ligament injuries, such as injury of the anterior cruciate ligament (ACL), a segment of the patellar tendon is frequently used (Jackson, et al. Amer. J. Sports Med., 18 (1):1-10 (1990)). Transplantation of autogenous grafts has been the current treatment of choice for cartilage and bone repair.
However, there are various problems associated with these treatments. For example, for autogenous tissue, key limitations are donor site morbidity where the remaining tissue at the harvest site is damaged by removal of the graft, and the limited amount of tissue available for harvesting. Allografts are an attempt to alleviate these problems. However, this type of graft is often rejected by the host body due to an immune response to the tissue. Allografts are also capable of transmitting disease. Although a thorough screening process eliminates most of the disease carrying tissue, this method is not 100% effective. Surgeons have looked to synthetic alternatives as a result of the limitations with conventional reconstructive graft materials.
Synthetic ligament grafts or graft supports include carbon fibers, Leeds-Keio® ligament (polyethylene terephthalate), the Gore Tex® prosthesis (polytetrafluoroethylene), the Stryker-Dacron® ligament prosthesis made of Dacron® tapes wrapped in a Dacron® sleeve and the Gore-Tex® ligament augmentation device (LAD) made from polypropylene. These grafts have exhibited good short term results but have encountered clinical difficulties in long term studies. Limitations of these synthetic ligament grafts include stretching of the replacement material, weakened mechanical strength compared to the original structure and fragmentation of the replacement material due to wear.
Natural ligaments are elongated bundles of collagenous soft tissue that serve, among other things, to hold the component bones of joints together. The desired characteristics for a ligament prosthesis include appropriate size and shape, biological compatibility, capability of being readily attached by the surgeon to the body of the patient, high fatigue resistance and mechanical behavior approximating that of the ligamentous tissue sought to be repaired or replaced.
Ligament constructs comprising collagen fibers, biodegradable polymers and composites thereof have been developed. Collagen scaffolds for ACL reconstruction seeded with fibroblasts from ACL and skin are described for example in Bellincampi, et al. J. Orthop. Res. 16:414-420 (1998) and PCT WO 95/2550. A bioengineered ligament model, which includes addition of ACL fibroblasts to the structure, the absence of cross-linking agents and the use of bone plugs to anchor the bioengineered tissue, has also been described (Goulet et al. Tendons and Ligaments. In R. P. Lanza, R. Langer, and W. L. Chick (eds), Principles of Tissue Engineering, pp. 639-645, R. G. Landes Company and Academic Press, Inc. 1997). U.S. Patent Application No. 20020123805 by Murray, et al. describes the use of a three-dimensional (three dimensional) scaffold composition which includes an inductive core made of collagen or other material, for repairing a ruptured anterior cruciate ligament (ACL) and a method for attaching the composition to the ruptured anterior cruciate ligament (See also U.S. Patent Application No. 20040059416). WO 2007/087353 discloses three-dimensional scaffolds for repairing torn or ruptured ligaments. The scaffold may be made of protein, and may be pretreated with a repair material such as a hydrogel or collagen. U.S. Patent Application No. 20080031923 by Murray, et al. describes preparation of a collagen gel and a collagen-MATRIGEL™ gel which is applied to a torn ligament for repair of the ligament. These collagen matrices are mostly monocomponent devices.
A number of multicomponent ligament prosthesis have been described (see, e.g. U.S. Pat. Nos. 3,797,047; 4,187,558; 4,483,023, 4,610,688 and 4,792,336). U.S. Pat. No. 4,792,336 to Hlavacek, et al. discloses a device with an absorbable component comprising a glycolic or lactic acid ester linkage, and the remainder of the device comprising a non-absorbable component. The device includes a plurality of fibers comprising the absorbable component which can be used as a flat braid in the repair of a ligament or tendon. The required tensile strength is obtained by increasing the final braid denier. U.S. Pat. No. 5,061,283 to Silvestrini discloses a bicomponent device comprising polyethylene terepthalate and a polyester/polyether block copolymer for use in ligament repair. U.S. Pat. No. 5,263,984 to Li, et al, describes prosthetic ligament which is a composite of two densities of bioresorbable filaments. There is still a need for a device for repair of articular tissue such as the ligaments and tendons, with improved strength retention, load bearing capacity and ingrowth of new tissue.
It is an object of the present invention to provide a biocompatible device for repair, regeneration or reconstruction in articular injury which provides both mechanical and structure repair as well as forms a scaffold for ingrowth of cells to foam new tissue.
It is still another object of the present invention to provide a method for producing a device for repair, regeneration or reconstruction of articular injury which results in improved strength retention and ingrowth of new tissue.
It is also an object of the present invention to provide a method for repair, regeneration or reconstruction in articular injury which comprises implanting at the damaged area, a biocompatible polymeric device which supports ingrowth of cells and formation of new tissue, while simultaneously providing mechanical and structural support.